Extensive intramolecular π-conjugation is considered to be requisite in the design of organic semiconductors. Here, two inkjet pigments, epindolidione and quinacridone, that break this design rule are explored. These molecules afford intermolecular π-stacking reinforced by hydrogen-bonding bridges. Air-stable organic field effect transistors are reported that support mobilities up to 1.5 cm(2)/Vs with T80 lifetimes comparable with the most stable reported organic semiconducting materials.

The causes of the spectral instability of poly[9,9‐dioctylfluoren‐2,7‐diyl‐co‐2′,7′‐spiro(cyclohexane‐1,9′‐fluorene)] during thermal annealing in air, which leads to a green photoluminescence (PL) emission band, are investigated. The Igreen/Iblue ratio evolution (I = intensity) is found to be independent of the amount of monoalkylfluorene defects, despite the fact that their presence might be regarded as a trigger for the radical process leading to polymer degradation in the presence of a trace amount of metal catalyst. Furthermore, the absence of a correlation between the degree of oxidation of the material and the Igreen/Iblue ratio indicates that the spatial disposition of fluorenones formed during the thermal degradation of the material, rather than their amount, is to be strictly related to the Igreen/Iblue ratio. The evidenced formation of fluorenone agglomerates, which could be considered the cause for the consistent increase in the Igreen/Iblue ratio during a thermal oxidation of a polyfluorene, confirms that the radical mechanism can also involve dialkylfluorene systems. Finally, the higher resistance to thermal degradation shown by spirocyclohexane fluorene units with respect to dioctylfluorene ones allows the synthesis of new, spectrally stable, fluorene‐based copolymers.

The PR2– group (the phosphanido group, according to the modern IUPAC rules) possesses a strong nucleophilicity, a high bridging tendency and a remarkable flexibility. This review addresses the issue of (phosphanido)platinum complexes, subdividing them into terminal and bridging species. Terminal (phosphanido)platinum complexes are usually prepared by deprotonation of a coordinated secondary (or primary) phosphane on a cationic PtII complex, by an appropriate base. The terminally bonded phosphanide group shows no tendency to form multiple bonds with platinum: in all crystallographically characterised Pt complexes, the terminal phosphanido P atom is pyramidal. Due to the high nucleophilicity granted by the presence of the active lone pair on P, terminal (phosphanido)platinum complexes react with molecules such as O2 and S8, and they can be used for the synthesis of dimetallic compounds upon reaction with suitable metal fragments. The known PtI phosphanido‐bridged complexes are dinuclear, diamagnetic and endowed with a strong Pt–Pt bond. The μ‐PPh2 bridge in PtI dimers arises often by (thermal) activation of the P–C bond in coordinated PPh3 or dppm. PtI phosphanido‐bridged complexes are also prepared by reaction of (dichlorido)platinum complexes with reagents such as Na, NaOH, alcohols. For such complexes a multifaceted reactivity, including the substitution of a terminal ligand, the reaction with electrophiles such as H+ and its isolobal analogues, the insertion into the μ‐P–Pt bond, has been reported. Hydridophosphanido complexes are formed by oxidative addition of a P–H bond onto zero‐valent Pt complexes, by protonation of PtI dimers or by action of BH4– on halido species. Dehydrochlorination of secondary (and primary) phosphane complexes gives chlorido complexes which are mostly prepared in the anti‐[(PRR′2)(Cl)Pt(μ‐PR″2)]2 geometry. Chiral complexes are obtained when asymmetric phosphanido P atoms are present in the molecule. A rich coordination chemistry has been developed on organometallic phosphanido Pt complexes bearing the pentafluorophenyl group. In this framework, a great number of Pt complexes of various nuclearity have been crystallographically characterised and their reactivity towards oxidants studied. The class of polynuclear phosphanido Pt complexes is represented by triangulo species, in which the bridging phosphanide group is typically μ‐PPh2 or μ‐PtBu2, by linear complexes of various nuclearity and by bent species stemming from the presence of a triply bridging diphenylphosphanido ligand in the molecule. Applications of phosphanido Pt complexes in catalysis and materials chemistry are also discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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